Conventional data communications cables often include multiple twisted pairs within a protective outer jacket. Typical data cable constructions use pair separation fillers made from solid dielectric materials such as polyolefin and fluoropolymers to provide physical distance (i.e., separation) between the pairs within a cable, thereby reducing crosstalk. In the event a portion of the cable ignites, it is desirable to limit the amount of smoke produced as a result of the melting or burning of the non-conductive portions (e.g., separation filler) of the cable. It is also desirable to prevent or limit the spread of flames along the cable from one portion of the cable to another.
Turning to FIG. 1, a cross-sectional view of a conventional communications cable 100 showing a star-shaped separator 104 composed of solid filler material is shown. Cable 100 includes four twisted pairs of conductive wires 102. The twisted pairs 102 are separated by the conventional “star” shaped filler 104 which is formed of solid dielectric materials, such as polyolefin and fluoropolymers, to provide physical distance (i.e., separation) between the pairs 102 within the cable 100. An outer jacket 106 surrounds the twisted pairs 102 and filler 104.
One disadvantage to the use of separation fillers is that typical filler materials, such as fluoropolymers, have poor smoke- and flame-retardant properties. Therefore, the added material of the filler within the cable construction increases the amount of smoke that is emitted as well as the distance that flame travels along a burning cable. In order to mitigate those drawbacks, some manufacturers add flame retardants and smoke suppressants to the polyolefin and fluoropolymer materials used in the conventional fillers. However, smoke suppressants and flame retardants often increase the dielectric constant and dissipative factors of the filler, thereby adversely affecting the electrical properties of the cable construction by increasing the signal loss of the twisted pairs within close proximity to the filler.
As a result, some conventional manufacturers may “foam” the fillers in order to reduce the amount of material, where a foamed filler material is any material that is in a lightweight cellular form resulting from introduction of gas bubbles during manufacture. However, conventional foaming methods can only reduce the amount of material by no more than approximately thirty percent. Another drawback to foamed fillers is that during cable processing or manufacturing, crushing or deformation of the foamed fillers may occur resulting in compacted filler material and less separation between twisted pairs. As a result, foamed fillers often possess an undesirable imbalance between electrical and smoke/flame retardant properties.
Accordingly, in light of the above drawbacks associated with conventional fillers, separators, and cables, there is a need for a separator used in a data communications cable that reduces crosstalk between twisted pairs within the cable while simultaneously improving the flame spread and smoke emission properties of the cable.